Carbon Fiber vs. Fiberglass

[Trilody]

I've been researching the technical qualities of carbon fiber fairly extensively. In particular, I've been attempting to find technical and scientific comparisons with fiberglass. There is some, but much of it is anecdotal or application specific and very little seems to relate to marine application, except in the case of kayak building, where carbon fiber is considered a superior material to fiberglass.

In the case of carbon fiber's application in the construction of high performance vehicles and parts, as well as in airplanes there is some further information, but its not readily transferable to marine applications. The most famous case is Boing's decision to bet the entire company on carbon fiber in the development of its new generation dreamliner, the 787. I presume that they chose to build their next generation jet liner out of carbon fiber instead of fiberglass, for good reason.

So, my question - what insight or knowledge do you have on the use of carbon fiber in boat building, as it relates to substituting fiberglass for this newer and stronger than steel fibre (for its weight)?

In particular, has anyone had any practical experience in using it and what were the strength advantages?

I understand the issue that carbon fiber does not allow natural wood color and grain to present through the material, but are their issues with it's relative hardness, compared to plywood, for instance?

Thanks for your thoughts,

Richard

[Bill Edmundson]

Carbon gives a light, strong and stiff lay-up. But expensive.

Bill

[Soloboat]

Check out Gerr's The nature of boats one chapter looks at comparative strengths and merits of boat building materials including carbon fibre

[kens]

Check out Gerr's The nature of boats one chapter looks at comparative strengths and merits of boat building materials including carbon fibre

I was gonna go there and Denzil beat me to it.

Gerr goes on to say that wood beats carbon fibre also.

Boeing, I doubt, is betting the whole company on the 787. Few companies have as good engineers as Big Blue (Boeing). There has been many aircraft already done in carbon fibre. Beech Starship was the 1st one FAA certified. Burt Rutan has long been a pioneer in composites. Boeing is merely going ahead with a larger scale production from what others have previously pioneered.

I think it all comes down to labor costs involved. If you take plain fiberglass and vacuum bag it along with all the associated high-skill labor, then it will be stronger/lighter than a simple hand-laid laminate of carbon with unskilled labor.
Most of us on this forum already know that our plywood boats are lighter than fiberglass counterparts. Therefore it would take carbon fibre construction to compete with our simple plywood hulls, right?
Gerr takes the idea one step further in that you apply all the high-tech labor technology available, and put that towards wood, and wood beats carbon fibre.

[upspirate]

Guys,I think what he was asking was about using CF cloth instead of FG cloth on his wooden tug build for strength and abrasion resistance, not a total lay-up of CF.

I could be wrong there....

[Trilody]

Thanks for your input. I'll have to find Gerr and start reading.

Pirate, that's the idea, yes, I'm looking to substitute FG for CF, not on the Tug, mind you, as FG will be just fine on that semi-displacement hull, but on the plans I'm making for next season's boat build - a more high performance type hull.

Re the Boeing thing, that was from the "Legends of Flight" movie in which the head of the Dreamliner project described the high stakes gamble they took, not me.

One of the key issues that I have is how well CF works with plywood. There was discussion on some homebuilder aviation forums that talked about how the superior strength of CF was in effect a liability, since the softer associated material transfers stresses to the harder material and thereby causes the break in the CF. In other words, would plywood's relative flexibility transfer stresses to the more brittle CF, causing it to crack, as compared to say FG?

These are the sorts of things I'm trying to understand, but I suspect that there haven't been any objective studies on the use of CF in association with marine plywood and for the marine environment.

Thanks again and more insight and knowledge is welcome, as this is an important bit of information that I'm pursuing.

Re: the Tug, she'll be flipped on Saturday and be prepped for a standard fiberglass covering. There's a good possibility that she'll see water sometime during this boating season.

Cheers,

Richard

[upspirate]

Glen-L sells the book:

http://www.boatdesigns.com/The-Nature-o ... fo/12-450/

[Trilody]

Perfect, and thanks Pirate.

[upspirate]

Your welcome!

[kens]

Boeing also said that risked everything when they built the 747, the 767, the 777, the 787, ......727,......etc., etc.

BTW, what is the last design of Boeing hand drawn with engineers, pencils, & slide rules?

[Trilody]

I got my answer today. Care of Rick at Noah's Marine Supplies; using CF cloth on plywood is not advisable. CF is extremely strong and stiff and of course light weight and typically used on say foam core or on its own, but not in a manner in which you'd typically use FG cloth in plywood boat construction.

Basically, the same issue which I was reading about on the airplane builder forum applies. CF on plywood would likely crack or at best delaminate if used together on a higher performance type hull. Seems logical too. Plywood has relatively greater flex in it, while CF is comparatively brittle.

It probably would be fine on my little tug (though I had no intention of using it there), but wouldn't add anything that plain old FG cloth can deliver in protection from abrasion, but would cost a great deal more.

So I'm back to designing my next hull with FG cloth on plywood and pleased to have ruled out the CF option.

Cheers,

Richard

[upspirate]

Thanks for that info Richard...as you can see,we didn't know the answer,but now do!!

[Trilody]

NP Pirate. Happy to share anything that I learn and to learn more in the process. I suppose that's why this forum is so valuable and addictive to people who want to know more about the art and science of boat building.

You're a great contributor of knowledge on this site and thank you for that.

Richard

[Andy Garrett]

Interesting discussion... Though it seems that the question was answered, I'll toss this in.

I live in Wichita, so Boeing, Hawker-Beech, Learjet, Cessna, Spirit, Airbus, and dozens of other aviation companies are litterally right down the street. This town knows a thing or two about composites--can't help but soak up a bit of knowledge just living here.

I've used CF in knifehandles and understand the nature of the product, though I have no high stress application experience.

CF is superior to FG in most applications precisely because it IS NOT too stiff and brittle. The fiber itself is strong and flexible at the individual strand level, without being subject to 'streching'. FG is subject to snapping and is considerably brittle at the strand level. After all, it is glass.

As for marine applications of CF, there are plenty! High performance sailboats frequently use a hollow CF mast because it is light strong and flexible. Any over-stiff material would be subject to snap under that kind of stress.

As for laminating CF to a hull, I would assume that the bonding properties would be a function of the resin system used. The type of fabric used is important because it must give with the wood substrate to some extent. Perhaps this is dictated by the weave type. I know that they sell CF fabric it several weave types for this very reason. Maybe FG works best on a boat hull, because the strands are actually breaking at the individual strand level, rather than 'giving'. As long as the epoxy holds the glass to the hull, we still get the abrasion resistance, yes?

I think the right weave type in CF or even Kevlar (which has LOTS of give), with the right resin system could yield excellent abrasion resistance on a high performance hull, but that's just my gut feeling. I'll be sticking to FG on my slow little Zip.

[upspirate]

NP Pirate. Happy to share anything that I learn and to learn more in the process. I suppose that's why this forum is so valuable and addictive to people who want to know more about the art and science of boat building.

You're a great contributor of knowledge on this site and thank you for that.

Richard

Thanks!